Demonstration for the death of prosecutor Alberto Nisman. Quinta de Olivos. Buenos Aires. Photo taken from the account of JMalievi in Flickr under Creative Commons license.

Alberto Nisman was one of Argentina's most famous federal prosecutors. For more than ten years, he was the chief investigator of the 1994 car bombing of a Jewish center in Buenos Aires, which killed 85 people and injured another 300—the worst terrorist attack in Argentina's history. As with his investigation of the 1994 bombing, Nisman's death on January 18, 2015, left the country with more questions than answers.

The first person to break the news of Nisman's death was journalist Damián Pachter, who made the announcement on Twitter:

They found Prosecutor Alberto Nisman in the bathroom of his home in Puerto Madero in a pool of blood. He was not breathing. Doctors are there.

Patcher left Argentina days later, “fearing for his safety.” He currently resides in Israel. Nisman's unexpected death galvanized people around the world, as shown in the following Twitter map:

The worldwide impact of #MuertedeNisman hashtag was reflected on this visualization developed with the tool CartoDB.

Nisman was found dead at his home in Buenos Aires beside a handgun, just hours before he was due to appear before Congress. Internet users have speculated rampantly about whether it was suicide or homicide. The incident has unsurprisingly become politicized:

According to Argentinian police, Nisman, age 51, committed suicide just a few hours before he was supposed to speak to Congress and present his case against President Cristina Fernández de Kirchner, whom Nisman accused of having reached a secret agreement with Iran to protect the alleged perpetrators of the 1994 attack.

On the morning of July 18, 1994, about 300 kilograms (660 pounds) of explosives were detonated in front of the Argentine Israelite Mutual Association building. Local and international investigators later determined that Iranian officials with ties to the Lebanese group Hezbollah most likely masterminded of the attack.

The Iranian government rejects the accusations, however, and has refused repeatedly to cooperate with investigators, despite a denunciation from the United Nations.

In 2013, Argentina and Iran signed an agreement called the “Memorandum of Understanding,” which created a “Truth Commission” to clarify the events of 1994. Argentina's Jewish community, the largest in Latin America, did not welcome the agreement, which it said would fail due to Tehran's lack of interest. Indeed, the Iranian parliament would not approve the memorandum, as President Mahmoud Ahmadinejad never submitted it for review.

Nisman argued that the agreement was signed to “fabricate the Iran's innocence” and facilitate the commercial trade of grains and meat in exchange for energy between the two countries.

The only person ever prosecuted for the bombing was Carlos Telleldín, who sold the truck that carried the suicide bomber to the target. Those behind the attack remain at large.